A challenging case: A German shepherd with a decreasing appetite and azotemia - Veterinary Medicine
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A challenging case: A German shepherd with a decreasing appetite and azotemia
Obtaining samples by using ultrasound guidance and re-reviewing results helped these clinicians identify a rare and easily overlooked disease.


VETERINARY MEDICINE


Paecilomycosis typically has a chronic course with clinical manifestations dependent on the affected organs. The most commonly reported clinical signs are fever, ataxia, paresis or paralysis, weight loss, and lameness3-16 ; however, vestibular signs, bilateral deafness, generalized seizures, chorioretinitis, and anemia have also been reported. All dogs reported to have paecilomycosis showed rapidly progressing clinical signs and were eventually euthanized.3-16

Systemic paecilomycosis affecting the kidneys has been previously reported in dogs. Renal lesions similar to the ones seen in our patient were observed in many of the reported cases of paecilomycoses,4,8-11,16 but the clinical signs associated with renal dysfunction were not present in any of the affected dogs. In our patient, renal involvement was manifested both clinically and histologically. Biopsy samples showed severe membranoproliferative glomerulonephritis and multifocal, pyogranulomatous nephritis. The most commonly encountered hematologic abnormalities in dogs with paecilomycosis are hyperglobulinemia,6,7,11,16 eosinophilia,5-7 and hypoalbuminemia.6-8 This dog exhibited hyperglobulinemia and eosinophilia.

In the published veterinary cases of paecilomycosis, most animals did not have obvious immunosuppressive conditions (e.g. terminal illness, immunosuppressive drugs) or an alteration of the normal microbial balance by prolonged antibiotic use. German shepherds have a relative deficiency of immunoglobulin A (IgA) compared with other purebred and mixed-breed dogs,20 supporting the possibility that local immunity might be defective in German shepherds and may play a role in the development of fungal infections. IgA is a component of mucosal surface immunity, which includes the skin and the respiratory, digestive, and reproductive tracts. The total serum IgA concentration was not measured in this dog.

Paecilomyces species infection is often difficult to diagnose because its presentation and the histologic appearance of the fungus are similar to the better-known Aspergillus species. In the localized form, paecilomycosis may be especially difficult to diagnose, but it is important to distinguish an active fungal infection from another disease with fungal contamination. The precise identification of a fungus can be made only by isolation in a pure culture. In this case, a microscopic examination of the urine collected in the renal pelvis demonstrated numerous fungal elements, while the biopsy sample obtained with ultrasound guidance demonstrated few fungal elements. Many of the histologic features were compatible with some of the more invasive and commonly encountered fungi such as Aspergillus species. However, after Paecilomyces species was cultured from the urine sample collected by pyelocentesis and the histologic samples were re-reviewed, some morphologic features were noted to be indicative of Paecilomyces species rather than Aspergillus species. Thus, fungal organisms may be difficult to identify based on histologic appearance, particularly with a limited sample size and the presence of few organisms, such as occurred with these core biopsy samples.

If systemic mycosis is suspected, especially in a mature German shepherd, obtain a urine sample in a sterile manner to look for fungal hyphae, which can often be identified in urine,15,19 and to perform a fungal culture. In addition, perform a cytologic examination and fungal culture of the lesion itself.15,19

In most veterinary reports, paecilomycosis is definitively diagnosed on postmortem examination.3-7,9-12 In this dog, we based our diagnosis of renal Paecilomyces species infection on findings from samples taken antemortem. Most of the findings in our patient suggested chronic pyelonephritis or glomerular, tubular, or interstitial nephritis21 ; however, the presence of echogenic material within the proximal collecting system (pelvis, proximal ureter) was unusual. Ultrasound-guided pyelocentesis is a safe procedure with which to collect urine samples for culture.22,23

Treating this rare disease is challenging. Several antifungal medications have been used, including itraconazole, ketoconazole, and amphotericin B. In vitro susceptibility testing in one study suggested that amphotericin B and itraconazole are optimal choices for treating paecilomycosis in veterinary patients.11 However, susceptibility-testing results often do not correlate with clinical outcome.2,11,18 For this reason, it is difficult to make specific recommendations regarding treatment. Nevertheless, sensitivity testing of each clinical isolate of Paecilomyces species is justified because it indicates a definite trend in susceptibility of the organism to antifungal agents.16


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Source: VETERINARY MEDICINE,
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